The present invention relates generally to the fabrication of semiconductor devices, and more particularly to magnetic random access memory (MRAM) devices.
Semiconductors are used for integrated circuits for electronic applications, including radios, televisions, cell phones, and personal computing devices, as examples. One type of semiconductor device is a semiconductor storage device, such as a dynamic random access memory (DRAM) and flash memory, which use a charge to store information.
A more recent development in memory devices involves spin electronics, which combines semiconductor technology and magnetics. The spin of an electron, rather than the charge, is used to indicate the presence of a xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d. One such spin electronic device is an MRAM device, which includes conductive lines positioned perpendicular to one another in different metal layers, the conductive lines sandwiching a magnetic stack. The place where the conductive lines, e.g., wordlines and bitlines, intersect is called a cross-point. A current flowing through one of the conductive lines generates a magnetic field around the conductive line and orients the magnetic polarity into a certain direction along the wire or conductive line. A current flowing through the other conductive line induces the magnetic field and can partially turn the magnetic polarity, also. Digital information, represented as a xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d, is storable in the alignment of magnetic moments. The resistance of the magnetic component depends on the moment""s alignment. The stored state is read from the element by detecting the component""s resistive state. A memory cell array is generally constructed by placing the conductive lines and cross-points in a matrix structure having rows and columns.
An advantage of MRAM devices compared to traditional semiconductor memory devices such as DRAM devices is that MRAM devices are non-volatile. For example, a personal computer (PC) utilizing MRAM devices would not have a long xe2x80x9cboot-upxe2x80x9d time as with conventional PCs that utilize DRAM devices. Also, an MRAM device does not need to be powered up and has the capability of xe2x80x9crememberingxe2x80x9d the stored data.
Because MRAM devices operate differently than traditional memory devices, they introduce design and manufacturing challenges.
Preferred embodiments of the present invention achieve technical advantages as a plate-through technique for fabricating metal hard masks for patterning magnetic stack material of MRAM devices.
In one embodiment, disclosed is a method of fabricating a resistive semiconductor memory device, comprising forming a plurality of first conductive lines, forming a magnetic stack material over the first conductive lines and depositing a resist over the magnetic stack material. The method includes patterning the resist, removing portions of the resist to expose regions of the magnetic stack material, and depositing a hard mask material over the exposed regions of the magnetic stack material to form a hard mask.
In another embodiment, disclosed is a method of fabricating a MRAM device, comprising providing a workpiece, depositing a first insulating layer over the workpiece, forming a plurality of first conductive lines within the first insulating layer, and depositing a magnetic stack material over the first conductive lines and first insulating layer. The method includes depositing a resist over the magnetic stack material, patterning the resist, removing portions of the resist to expose regions of the magnetic stack material, and depositing a hard mask material over the exposed regions of the magnetic stack material through the resist to form a hard mask. The resist is removed, and the hard mask is used to pattern the magnetic stack material and form magnetic tunnel junctions. (MTJ""s).
Advantages of embodiments of the invention include providing a method of forming a hard mask over a magnetic stack material layer of an MRAM device that does not require a metal etch process. The pattern shape of a lithography mask pattern for MTJ shape is better preserved compared with methods of forming bard masks that require a metal etch process. Hard mask formation using metal etch processes typically have basics, resulting in patterns that are smaller than desired, and corner rounding of features. Forming a hard mask for a magnetic material stack using a plate-through process in accordance with embodiments of the invention provides a method of precisely patterning of MTJ""s an MRAM device. Further advantages include process simplification and better contraindication control. The lithography process window is improved, because the process window for printing voids in a material is, in general, larger than process windows for printing pillars.